雙語暢銷書《艾倫圖靈傳》第8章:水銀延時線(18)
Lacking such cathode ray tube storage, he had to plump for the mercury delay lines, not with any great enthusiasm, but because they were already working.
They held the obvious disadvantage, from the point of view of accessibility, of involving a delay.
從可讀取性和延遲的角度來看，水銀延遲線有明顯的劣勢。His plan was for a delay line to hold a sequence of 1024 pulses, so it was like chopping up the 'tape' of the Universal Turing Machine into segments each of 1024 squares in length.
按照圖靈的計劃，每條延遲線要維持一串1024個脈衝的序列，這就相當於把通用圖靈機的紙帶分段，每段1024個方格。
It would take an average of 512 units of time to reach a given entry. However, this was an improvement upon the 'papyrus scroll'.
這將花費平均512個單位的訪問時間，來讀取一個特定的存儲項，與埃及沙草紙卷相比，這是很明顯的進步。As for the other most important aspect of the machine, this was the 'Logical Control'. It corresponded to the 'scanner' of the Universal Turing Machine.
另外一個重要的問題就是邏輯控制，相當於通用圖靈機的"掃描器"。The principle was simple: 'The universal machine has only to keep looking at this description'—that is, at the instructions on its tape—'to find out what it should do at each stage.'
它的原理很簡單，通用機一直按照描述數，也就是紙帶上的指令，來決定每個時刻應該做什麼。So the Logical Control was a piece of electronic hardware which would contain two pieces of information: where it was on the 'tape', and what instruction it had read there.
所以"邏輯控制"就是一個帶有兩項信息的電子硬件，這兩項信息是：它現在位於紙帶的什麼位置，以及它在那裏取到了什麼指令。The instruction would take up thirty-two 'squares' or pulses in a delay line store, and might be of two kinds, in the design that he proposed.
按照圖靈的設計，一條指令佔32個方格，或者說32個脈衝。It might simply cause the 'scanner' to go on to another point of the 'tape' for its next instruction.
指令有兩種，一種是使掃描器移到某個方格去讀下一條指令，Alternatively, it might prescribe an operation of adding, multiplying, shifting or copying, of numbers stored elsewhere on the 'tape'.
另一種是描述某種操作，比如對某個方格中的數進行加、乘、移位或複製。In the latter case, the 'scanner' was to move to the next point on the 'tape' for its next instruction.
在第二種情況下，掃描器會自動移到相鄰的方格去讀取下一條指令。None of this involved anything but the reading, writing, erasing, changing of state, and moving to left and right,
這些操作只涉及讀取、寫入、清除、改變方格的狀態，以及左右移動掃描器，that was to be done by the theoretical Universal Turing Machine working on the description numbers on its tape—except that there were special facilities added so that addition and multiplication could be achieved in only a few steps, rather than with thousands of more elementary operations.
這都與理論中的通用圖靈機完全一致。唯一的不同就是引入了特殊的計算部件，使加法和乘法可以在幾步內完成，而不是幾千步。
